Lubricant composition



United States Patent Ofiiice 3,1 10,670 Patented Nov. 12, 1963 3,110,670 LUBRICANT COMPOSITION iohn W. Nelson, Lansing, lll., assignor, by mesne assignments, to dinclair Research Inc., New York, N.Y., a

corporation of Delaware No Drawing. Filed Aug. 3, 195% Ser. No. 831,051

6 Qlairns. (Cl. 252-336) This invention is drawn to a novel composition of matter, to Wit: the barium salts of primary N-alkyl amides of benzene hydroxy carboxylic acids and lubricants containing these salts.

US. Patent 2,337,380 describes a lubricating oil containing calcium N-diamyl salicylamide which has improved properties with respect to oxidation. However, the barium salt of this amide is not soluble in oil to a material extent and ;it is frequently desirable to add an oxidation inhibitor as the barium salt.

As is well known, mineral oil based liquid lubricantsespecially motor oils-suffer from the effects of oxidation when used in high temperature applications. The oxidation of the parafiin hydrocarbons included in a mineral oil lubricant yields a number of organic acids. Naphthenic hydrocarbons probably oxidize and yield oxy productsaoids, alcohols, ketones, etc.in a manner very similar to the parafiins. Aromatic hydrocarbon constituents of lubricating oils are readily oxidized the oxygen first attacking side chains to yield acids and acidic oxy products of the same general types as the paraffins with subsequent oxidation of the aromatic ring to form complex condensation and polymerization products which tend to be oil-insoluble and which are called sludges.

Many turbine oils and greases contain oil-soluble organic amines and phenol derivatives such as phenyl-anaphthylamine and fl-naphthol but these additives are deemed to be essentially low temperature inhibitors being etfective only at temperatures below about 200 or 250 F. and therefore are not suitable for the conditions of temperature and agitation which prevail in engines operating under heavy loads. Mineral oil lubricants designed for high temperature use generally contain sulfur and/ or phoeohorus compounds to combat oxidative eifects but it is not clear whether these additives actually inhibit the oxidation itself or morely prevent oxidation products from harming the machinery lubricated since these materials also usually have a detergent function serving to keep engine parts somewhat free from resin and varnish deposits caused by sludge in the lubricant. Some additives which have been used are aromatic and aliphatic sulfides such as alkyl phenol sulfides, alkyl and aryl phosphites, salts of alkyl phosphoric acids, dithiophosphates, etc., and marry of the inhibited motor oils now on the market contain one kind or anothpr of these additives.

in addition, the acidic nature of the oxidation products of a mineral oil lubricant has prescribed the use of basicacting additives for the oil. For this reason salts of the additives mentioned above with group II metals have received widespread attention and significant use as inhibitor-detergent additives. Barium is particularly favored as the metal salt-former since it usually can be included in the salt in greater quantities than other group II metals to give a more basic-acting additive, but barium salts of common inhibitors are frequently not soluble in oil. The oil-solubility appears to be achieved only in a limited class of the barium salts of common inhibitors, and these are frequently quite expensive.

The novel barium salts of primary N-alkyl amides of this invention have been found to be relatively low-priced inhibitors of the oxidative effects or" high temperatures on lubricants. The effective amount required is small and the additives are frequently compatible, i.e. soluble, miscible or dispersible, per se in the liquid oil lubricants; that is, they do not require the presence of other additives to exercise a compatibilizing effect on them and they do not precipitate on standing. Some of the amides may become compatible due to the presence of other additives in the lubricant. These oil-compatible barium primary N-alkyl amides show efiiciency as inhibitor-detergents in concentrations as low as about 0.02 weight percent or less in oils of lubricating viscosity. A concentration of 0.01 to 0.1% is preferably used and seldom would the amount be above about 2 to 5%.

Since the sulfur and phosphorus compounds conventionally used in lubricants impart extreme pressure resistant, anti-oxidant and detergent qualities to the lubricant these materials are preferably not eliminated entirely from lubricants which use the novel barium compounds of this invention, although the quantity of these sulfur and phosphorus additives may be sharply reduced. Oxidation tests indicate as much as a 60% reduction in viscosity rise and lower pentane insolubles in liquid lube oil blends containing reduced levels of barium sulfonate and zinc dithiophosphate when the barium amides of this invention are used.

Barium primary N-alkyl amides may be prepared using the process of copending Nelson application Serial No. 810,531, filed May 4, 1959. The process provides for the direct amidization of hydroxy benzene carboxylic acids with amines using a catalytic amount of a boron oxide, such as boron trioxide or its hydrate, boric acid, in the reaction. To produce the oil-compatible material of this invention, a primary aliphatic amine is used which has a carbon content of about 8 to 32 atoms and generally the hydrocarbon chain of the amine will not contain less than 12 nor more than 20 carbon atoms. The carbon chain can be saturated or unsaturated.

Some amines which can be used to supply the amide portion of the novel compounds of the invention are com mercially available fatty amines such as: Armeen HT, 21 hydrogenated tallow amine comprising approximately 71% octadecyl, 24% hexadecyl, 3% octadec-enyl and 2% tetradecylamine; Armeen HTD (distilled Armeen HT); Ar-meen O, a mixture of oleyl, 6% linoleyl, 5% hexadecyl, 4% tetradecyl and 1% stearylarnines; Armeen OD (distilled Armeen O); Armeen 18D, distilled octadecylamine; Armeen C, a mostly C amine derived from coconut; Armeen CD (distilled Armeen C); Alamine H2613, another distilled tallow amine; Prirnene 81 R, a mixture of branched-chain amines containing 12 to 14 carbon atoms; andPrimene IMT, a mixture of branched chain primary amines containing 18 to 21 carbon atoms.

Although not all of these amines provide oil-solubility to the barium amide salt, such salts may be used in greases or in liquid lubricants Which contain additives such as mahogany sul-fonates, dithiophosphates, etc., which exert a solubilizirig effect on these amide salts. Aliphatic primary diamines, such as those commercially available in the Duomeen series which have the requisite carbon content are also suitable materials for amidization by the process of this invention. For example, Duomeen T, a hydrogenated reaction product of tallow amine and acrylonitrile, having a 32 to 50 iodine value and the structure R-NHCH CH CH NH where R is an alkyl group of 16 to 18 carbon atoms obtained from tallow, may be used. Sulfurized amines also may be used when it is desired to increase the sulfur content of the finished lubricant, for example, to improve its extreme pressure and other properties. Unsaturated amines, such as Armeen may easily be sulfided by reaction with elemental sulfur or sulfur yielding compounds at an elevated temperature.

The hydroxy benzene carboxylic part of the amide is the residue of an acid having one or more carboxylic acid substituents on the benzene nucleus and one or more hydroxy substituents on the nucleus. Preferably a hydroxy group is ortho to a carboxyl group. Hydroxy toluic acid, halo-, sulfoand amino-hydroxy benzene acids, as well as salicylic acid, to which particular attention is given, may be used so long as the compound is not decarboxylated under the reaction conditions. Disubstituted benzene acids as well as hydroxy benzoic and phthalic acids, etc., may be used but long-chain aliphatic substituents may prolong the reaction time unduly, so that lower-alkyl substituted benzene hydroxy carboxylic acids make better starting materials.

The acid may be represented structurally by the formula:

(COOH)m where m and n are each one or more, preferably not more than 2, the amide being CONHR (COOH)m1 where R is a hydrocarbon radical of 8 to 32 carbon atoms, preferably an alkyl including alkenyl of 12 to 20 carbon atoms, or its equivalent, as described above; that is, -NHR is the residue of a primary amine. The barium salt may neutralize one or more of the hydroxyl groups of the amide and may link two aromatic amide molecules.

The amidization reaction is performed readily at temperatures greater than about 160 F. up to the degradation temperature of the reactants or products. An upper temperature limit of about 300 C. or more is usually satisfactory. The lower temperature limit is important from the standpoint of obtaining an oil-soluble product. The amidization is preferably conducted in the presence of a solvent or water-entraining agent such as toluene or xylene in an amount from about to 200% of the weight of the reactants. Apparently, exact equimolecular quantities of salicylic acid and amines are not required. The amide need not be purified before use as an oiladditive. The catalytic amount of boron oxide used in the reaction is usually about 0.5 to 15% or more of the weight of the reactants, preferably about 17% of boron trioxide, boric acid, or a mixture of the two.

The primary N-alkyl hydroxybenzamide may be converted to its barium salt by direct reaction of the amide with barium hydroxide. The hydroxide may preferably The barium may be used in a stoichiometric amount to produce the neutral salt or in an excess amount to give the basic salt. It is also possible to react the hydroxybenzamide with a simple alkali such as sodium or ammonium hydroxide to form the, for example, sodium phenolate, and thereafter react the phenolate with barium chloride to form the barium salt by metathesis.

The oil base stock which is given improved oxidation resistance by the inclusion of a barium primary N-alkyl amide is of lubricating viscosity and can be for instance a solvent extracted or solvent refined mineral oil obtm'ned in accordance with conventional methods of solvent refining lubricating oils. Generally, lubricating oils have viscosities from about 20 to 250 SUS at 210 F. The base oil may be derived from parafiinic, naphthenic, asphaltic or mixed base crudes, and if desired, a blend of solvent-treated Mid-Continent neutrals and Mid-Continent bright stocks may be employed. A particularly suitable base oil is a solvent treated Mid-Continent neutral having a viscosity index of about 95. Synthetic lubricants may also be improved by the presence of the novel inhibitor of this invention. Such synthetic lubricants include simple and complex esters of long-chain fatty acids with alcohols and glycols, esters of dibasic acids such as di-(Z-ethylhexyl) sebacates, adipates and the like, polymerized cracked wax, po'lyglycol esters, polyglycol ethers, polyglycol ether esters, etc.

As mentioned above, the novel inhibitor of this invention may be used in a lubricant in conjunction with sulfur and phosphorus compounds. One class of compounds in widespread use today are the metal dialkyl dithiophosphates, which can be included in the lubricant in amounts of from about 0.01 weight percent up to about 10 weight percent and which can be obtained from a Wide variety of diester dithiophosphonic acids conventionally prepared by reacting a sulfide of phosphorus, such as phosphorus pentasulfide, with an alcohol, phenol or meroaptan. The organic groups in the acid esters may be aryl, alkyl, aralkyl or cycloalkyl groups which contain from about 4 to 20 carbon atoms, preferably up to about 14 carbon atoms and may be further substituted in the organic portion. Suitable alcohols which may be used in preparing the acid esters include primary and secondary alcohols such as 2-methylamyl alcohol, 4-rnethylpentanol-2, 2- methylpentanol-l, Z-ethylhexanol, di-isopropyl carbinol, cyclohexanol, butanol-l and octadecanol-l, or mixtures such as of high and low molecular weight alcohol or mixtures such as hexanol-heptanol. Other hydroxy-containing materials which can be reacted with phosphorus sulfide include phenols and alkylated phenols such as dioctyl phenol, tri-isobutylphenol and the like. The metal thiophosphate is conventionally manufactured by oxide or hydroxide neutralization of the acid ester. A number of metals may be used to form the thiophosphate, among which are calcium, zinc, nickel, molybdenum and other polyvalent metals.

The alkaline earth metal sulfonates which may be used in lubricant compositions containing the novel primary N-alkyl amides of this invention are those which are soluble in the lubricant base oil and obtained, for instance, by neutralizing aromatic sulfonic acids with the hydroxides, chlorides, oxides or other inorganic compounds of the alkaline earth metals. The preferred aromatic sulfonic acids are the oil-soluble mahogany sulfonic acids which can be derived from the treatment of a suitable petroleum oil, such as a liquid petroleum distillate boiling in the range of about 600 to 1000" F., with fuming sulfuric acid or sulfur trioxide, separating the resulting acid sludge from the acid treated oil and recovering the mahogany acids contained in the acid treated oil. The useful mahogany acids generally have a molecular weight of from about 300 to 500 or more, and although their exact chemical structures may vary, it appears that such acids are composed to a large extent of sulfonated aromatic hydrocarbons having either one or two aromatic rings per molecule, possibly with one or more long-chain alkyl groups containing from about 8 to 30 carbon atoms attached to the ring nuclei. Other suitable aromatic sulfonic acids are the oil-soluble aryl sulfonic acids; such as benzene sulfcnic acids and naphthalene sulfonic acids, which include the oil-soluble alkylated aryl sulfonic acids in which the alkyl chain contains from 8 to 18 carbon atoms, for instance, dinonyl naphthalene sulfonic acid, and those prepared by reaction of paratfin wax alkyl chains of 20 or more carbons with aromatic nuclei which are then sulfonated by fuming sulfuric acid, e.g. wax substituted naphthalene. The aromatic oil-soluble sulfonic acids are conveniently employed as a concentrate in the hydrocarbon from which they are derived and are usually present in an approximate 10 to 30 weight percent concentration.

The alkaline earth metal sulfonates can be neutral or basic sulfonates; by basic sulfonates is meant those sulfonates in which the alkaline earth metal is present in an amount in excess of that theoretically required to react with the sulfonic acid from which it was made. For instance, when a basic barium sulfonate is employed, there are usually at least about 1.5 equivalents of barium in the sulfonate and in the case of basic calcium sulfonate at least about 1.2 equivalents of calcium. Usually the basic alkaline earth .metal sulfonates do not have to have more than equivalents of alkaline earth metal. Also suitable for inclusion are the oil-soluble carbonated neutral or basic alkaline earth metal sulfonates.

The sulfonates may be included in the lubricant in amounts ranging from about 0.01 weight percent up to about Weight percent and are advantageously employed in the oil solution in which they are prepared. If desired, the sul'fonates can be recovered by extraction with a low molecular weight alcohol, such as isopropanol or ethanol, followed by distillation for use in the oil-free form.

Other materials normally incorporated in lube oils to impart special characteristics can be added to the lubricant compositions of this invention. These include corrosion inhibitors, anti-wear agents, etc. The amount of these additives included in the composition usually ranges from about 0.01 weight percent up to about 10 weight percent, although the best multi-purpose gear oils require a combination of extreme pressure additives amounting to about 5 to 20% of the total weight of the lubricant, usually about 843%.

The following example shows the preparation of an N-alkyl salicylarnide and its barium salt.

EXAMPLE I Into a 3-liter, round bottom, 4-necked flask equipped with a voltage regulated heating mantle, thermometer, motor driven stirrer, reflux condenser and water trap were charged the following: 13 8 g. (1 mole) salicylic acid U.S.P. grade, 275 g. (1 mole) Armeen O and 100 g. commercial xylene. Heat was applied to the flask and agitation started. After eleven minutes the temperature was 224 C. and the xylene started to reflux. During the next 7 /2 hours 5 cc. water and 30 cc. xylene were removed through the trap. The xylene was. removed to increase the reflux temperature. The mass was then allowed to cool from 260 C. to 140 C., 4 g. boric acid were added, and heat was again applied. The mass was heated for an additional 16% hours during which time 7 g. of boric acid in increments of 4 and 3 g. were added.

The mass was then blown with nitrogen for minutes up to 285 C. The yield was 85.5% of theory. This product had a saponification number of 5.7, an acid number or" 4.4, a hydroxyl value of 191 and contained 0.61% boron. it was oil-soluble.

An oil-soluble barium N-alkyl salicylarnide was prepared from this amide as follows, using a Mid-Continent neutral solvent refined oil having a viscosity index of and a SUS viscosity at F. of 150. 'Into an open beaker on a hot plate equipped with a motor driven stirrer and thermometer, 920 g. of the oil described and 79 g. (0.2 mole) of the oleyl N-salicylamide described above were charged. The mixture was heated to 230 F. with stirring. Then 29 g. (0.1 mole) of barium hydroxide pentahydrate were added batchwise over 10 min. The rate of addition was determined by the amount of foaming. The color of the solution changed with the addition of the barium hydroxide firom tan to greenish to dark brown. The temperature was raised to 300-320" F. to insure dehydration. The mass was then cooled to 250 F., one weight percent Supencel filter aid was added, and the mass was filtered under vacuum.

The resulting solution contained 9.6% of the barium salt of N-oleyl salicylamide. The salt did not precipitate on standing. The solution contained 1.57 barium and 0.03% boron and had a base number to pH 4 of 19.9.

EXAMPLE II Table 1 Sample III IV V VI Amine Used Armeen HTD Armeen Alamine 18 D H261) Barium, percent.-. 1. 55 1. 86 l. 54 1.56 Boron, percent 0. 025 Base No. to pH 4 20. 9 22. 7 19. 4 19. 4

All of these salts were soluble, but precipitated from solution in the oil at this relatively high content.

Table II, below, shows the results of oxidation tests performed upon lubricant blends containing varying proportions of a barium N-tallow salicyla-mide similar to that of Sample III. The base liquid mineral lubricating oil was a blend containing 51% by volume of a solvent refined neutral distillate having a viscosity of 200 SUS at 100 F. and a viscosity index of 95, and 49% by volume of a solvent refined Mid-Continent residual oil having a viscosity at 100 F. of 1870 SUS and a viscosity index of 90. The blends contained varying amounts of a basic barium mahogany sulfonate made by sulfonat ion with sulfur triox-ide of a dewaxed Mid- Continent lubricating oil traction having a viscosity of 250 SUS at 100 F. and a 70 viscosity index, and then neutralized with barium hydroxide and added to the minerol oil base as a 15 to 20% concentrate in its starting oil. The blends also contained varying amounts of zinc di-(2-methyl,pentanol-4), dithiophosphate diester added as a 50% concentrate in mineral oil, as well as 0.005% of a silicone anti-foaming agent. The results obtained using a lubricant without the novel additive of the invention, as well as a lubricant containing a higher proportion of the sulfonate are also reported. In each case, the amide was added as the 9.6% oil solution described above.

The test is one of oxidation characteristics of railway diesel lubricants (Railroad Oxidation Test) wherein five liters of oxygen per hour are bubbled through a 300 ml. sample of the lubricant in the presence of a steelbacked copper-lead catalyst.

Table II Sample 022 201 122 121 Additive (Percent):

Ba mahogany sulionate cncentrate 7 8 5.9 9 5 9 Zinc dithiophnsphatc concentrate 18 1.8 1 8 1 8 Ba N tallow salicylamide soluon 1.0 0. 5 KV/100 F" 112. 7 114. 6 101. 9 107. 9 21 11. 63 11. 75 10. 92 11. 24 Barium, Percent... 0. 51 0.39 0. 45 0. 4O Sulfur, PerceuL- 0. 36 0.35 0.36 0.32 RR Oxidation Tes SV/100 1*..- 96 1034 610 572 KV/100 F 1 207. 8 223. 1 131. 6 123. 4 Viscosity Rise, Percent 82 94. 5 29.0 14. 3 Catalyst Wt. Change, mg 2. 5 2. 9 13. 2 5. 5 Acid Number 6. 0 6. 1 6. 2 4. 6 Pentano Ins01., Percent.v 0. 9 2. 7 0.03 0. 01 Initial pH 1. 4 2. 2 1. 7 1. 7

1 Claim:

1. A lubricant composition of improved oxidation resistance consisting essentially of a base oil of lubricating viscosity and a small amount, effective to improve the oxidation resistance of the lubricant, of an oil-compatible barium salt of a primary N-aliphatic amide of a benzene hydroxy carboxylic acid where the aliphatic radical is a primary hydrocarbon radical of about 8 to 32 carbon atoms.

2. A lubricant composition of claim 1 where said barium salt is present in the amount of about 0.01 to 0.1% by weight.

3. The lubricant composition of claim 2 where the barium salt is of primary N-a-liphatic salicylamide where the aliphatic radical has 12 to carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,319,662 Cook et a1 May 18, 1943 2,320,228 Frey May 25, 1943 2,337,380 Finley et al. Dec. 21, 1943 2,764,614 Meyer Sept. 25, 1956 2,923,737 Ruschig et al Feb. 2, 1960 

1. A LUBRICANT COMPOSITION OF IMPROVED OXIDATION RESISTANCE CONSISTING ESSENTIALLY OF A BASE OIL OF LUBRICATING VISCOSITY AND A SMALL AMOUNT, EFFECTIVE TO IMPROVE THE OXIDATION RESISTANCE OF THE LUBRICANT, OF AN OIL-COMPATIBLE BARIUM SALT OF A PRIMARY N-ALPHATIC AMIDE OF A BENZENE HYDROXY CARBOXYLIC ACID WHERE THE ALPHATIC RADICAL IS A PRIMARY HYDROCARBON RADICAL OF ABOUT 8 TO 32 CARBON ATOMS. 